Question: Simplify the following expression: $q = \dfrac{1}{5z} - \dfrac{1}{6z}$
Solution: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5z$ and $6z$ $\lcm(5z, 6z) = 30z$ $ q = \dfrac{6}{6} \cdot \dfrac{1}{5z} - \dfrac{5}{5} \cdot \dfrac{1}{6z} $ $q = \dfrac{6}{30z} - \dfrac{5}{30z}$ $q = \dfrac{6 -5}{30z}$ $q = \dfrac{1}{30z}$